The invention relates to a process for manufacturing a layer arrangement having at least one bump, especially for a flip chip or similar connection, wherein several layers made of solid material are stacked into a layer stack. At least one recess is made in the stack transverse to the coating planes of the layers, into which a bump material is filled or applied. In addition, the invention relates to a layer arrangement with a layer stack having several layers made of solid material and having a recess extending transverse to the coating planes of the layers. A bump is arranged in the recess, which is provided especially for a flip chip or similar connection, and has a projection projecting on the surface of the layer stack, wherein the bump is made of a continuous one-piece bump material.
A process of this type and a layer arrangement manufactured according to it are already known from the book Flip Chip Technologies, John H. Lau, McGraw-Hill (1996). In the process, on a portion of the surface of a substrate made of a semiconductor material, an aluminum layer functioning as a connection path is first applied in certain areas. After that, the substrate is coated with a passivation layer, which covers the aluminum layer and the surface area of the substrate adjoining it. To expose the aluminum layer, a recess is then made in the passivation layer. On the aluminum layer and areas of the passivation layer laterally adjoining it, adhesive layers are applied, which are to improve the adhesion of additional layers to be applied and the bump material to be brought into the recess. Onto the adhesive layers, a copper layer is applied, which should make it more difficult for moisture to penetrate into the layer stack, and a gold layer is applied, which functions as an oxidation barrier. Next, the bump material is brought into the recess, for example, by vacuum evaporation through a metal mask, by plating, dispersion, or imprinting.
With the adhesive layers located between the substrate and the bump material, a better adhesion of the bump to the substrate is indeed achieved to a certain extent. However, the mechanical solidity of the layer arrangement manufactured according to the process is nevertheless in need of improvement. In practice, the moisture resistance of the layer arrangement has additionally proven to be problematic, since moisture can get under the bump material and can cause corrosion on the bump material and/or the layers of the layer stack. On the one hand, the mechanical solidity of the layer arrangement is thereby weakened, and on the other hand, the moisture can also change the electrical properties of the layer arrangement. In particular, there is the danger in a bump functioning as an electrical connection contact, that the moisture will cause electrical leak currents or short circuits.